SYNOPSIS

DESCRIPTION

setresuid() sets the real user ID, the effective user ID, and the saved
set-user-ID of the calling process.
Unprivileged user processes may change the real UID, effective UID, and
saved set-user-ID, each to one of: the current real UID, the current
effective UID or the current saved set-user-ID.
Privileged processes (on Linux, those having the CAP_SETUID capability)
may set the real UID, effective UID, and saved set-user-ID to arbitrary
values.
If one of the arguments equals -1, the corresponding value is not
changed.
Regardless of what changes are made to the real UID, effective UID, and
saved set-user-ID, the file system UID is always set to the same value
as the (possibly new) effective UID.
Completely analogously, setresgid() sets the real GID, effective GID,
and saved set-group-ID of the calling process (and always modifies the
file system GID to be the same as the effective GID), with the same
restrictions for unprivileged processes.

RETURNVALUE

On success, zero is returned. On error, -1 is returned, and errno is
set appropriately.

ERRORS

EAGAINuid does not match the current UID and this call would bring
that user ID over its RLIMIT_NPROC resource limit.
EPERM The calling process is not privileged (did not have the
CAP_SETUID capability) and tried to change the IDs to values
that are not permitted.

VERSIONS

These calls are available under Linux since Linux 2.1.44.

CONFORMINGTO

These calls are nonstandard; they also appear on HP-UX and some of the
BSDs.

NOTES

Under HP-UX and FreeBSD, the prototype is found in <unistd.h>. Under
Linux the prototype is provided by glibc since version 2.3.2.
The original Linux setresuid() and setresgid() system calls supported
only 16-bit user and group IDs. Subsequently, Linux 2.4 added
setresuid32() and setresgid32(), supporting 32-bit IDs. The glibc
setresuid() and setresgid() wrapper functions transparently deal with
the variations across kernel versions.